1. Technical Field
The present disclosure relates to lithium ion batteries.
2. Description of Related Art
Lithium batteries have small weight, high discharge voltage, long cyclic life and high energy density compared with conventional lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, and nickel-zinc batteries.
An anode of a lithium battery should have properties such as high energy density, low open-circuit voltage versus lithium metal electrode, high capacity retention, good performance in common electrolytes, high density (e.g. >2.0 g/cm3), good stability during charge and discharge processes, and low cost. Presently, the most common anode active material is carbonous/carbonaceous material such as natural graphite, artificial graphite, and amorphous-based carbon.
Carbonous/carbonaceous material has high theoretical specific capacity, but an SEI film forming process in the first cycle greatly decreases the real specific capacity, which is generally only about 200 mAh/g to about 500 mAh/g. Further, the potential difference between the carbonous/carbonaceous material and the lithium metal is not very large. Thus, the lithium ion battery may still form a short circuit between the cathode and anode caused by the lithium dendrite formed on the surface of the carbonous/carbonaceous anode. Furthermore, the coulombic efficiency of the lithium ion battery with the carbonous/carbonaceous anode is still relatively low.
Elemental sulfur has been reported to be a cathode active material of the lithium ion battery. Theoretical specific capacity of the elemental sulfur is about 1678 mAh/g, which is one of the highest known cathode active materials for the lithium ion batteries. However, the electric potential of sulfur versus lithium metal is relatively high, and sulfur has not been used as an anode active material of the lithium ion battery.
What is needed, therefore, is to provide a lithium ion battery having a relatively high coulombic efficiency, specific capacity, and safety.